Nutrafin Basix Vacation 3 Day Fish Feeders is specifically formulated to provide aquarium fish with nutritious food and multi-vitamins for up to 3 days. The slow-release blocks contain a rich diet complete with multi-vitamins for community aquariums up to 37.8 litres (10 U.S. gal.). For larger aquariums, simply add one block per 37.8 litres (10 U.S. gal.). Nutrafin Basix 7 Day Fish Feeder has been specifically formulated to provide food and multi-vitamins for your aquarium fish for up to 7 days. The slow-release feeder provides a varied diet of pellets and multi-vitamins for community aquariums up to 10 U.S. gallons (37.8 L). For larger aquariums simply add one block per 10 U.S. gallons (37.8 L).